3GPP LTE (Long Term Evolution) is the name given to a project within the Third Generation Partnership Program to improve the Universal Mobile Telecommunications System (hereinafter called UMTS) mobile phone standard to cope with future requirements. Some goals for the LTE project is to get improved efficiency, lower costs, improve services, make use of new spectrum opportunities, and better integration with other open standards. The LTE includes mostly or wholly extensions and modifications of the UMTS system.
As part of the new 3GPP (3GPP TS 36.300 v0.3.1 regarding contents in 3GPP TR 23.882 v1.6.1) architecture of the wireless radio network, the logic provided by a Radio Network Controller (hereinafter called RNC) in legacy of UMTS Terrestrial Radio Access Network (hereinafter called UTRAN) has been distributed to the enhanced radio base station (hereinafter called eNodeB) and the functional entities of the core network, CN. One functional entity is a Mobility Management Entity (hereinafter called MME or control plane node) which is a control plane node arranged to handle reliable control signaling from the eNodeB to another functional entity being a User Plane Entity (hereinafter called UPE or user plane node). The UPE is a user plane node handling unreliable signaling comprising payload data from the eNodeB to the UPE.
Traditionally NodeB is a term used in UMTS to denote the BTS (base transceiver station) controlling a cell in a cellular network. In contrast with GSM base stations, Node B uses WCDMA as air transport technology. As in all cellular systems, such as UMTS and GSM, Node B contains radio frequency transmitter(s) and the receiver(s) used to communicate directly with the mobiles, which move freely around it. In this type of cellular networks the mobiles cannot communicate directly with each other but have to communicate with the BTSs.
The eNodeB is an expanded NodeB arranged to handle wireless data communication that uses Orthogonal Frequency Division Multiple Access OFDMA as air transport technology. The OFDMA is arranged to replace the old CDMA and TDMA based systems. Each eNOdeB in the cellular network controls a cell in which the user equipment is positioned. When the user equipment moves from one cell to an adjacent cell a handover has to be performed where the communication path is directed from the previous NodeB (hereinafter referred to as source eNodeB) and the eNodeB (hereinafter referred to as target eNodeB) controlling the adjacent cell.
The MME share similarities with control plane of the Serving General Packet Radio Service (hereinafter called GPRS) Support Node (hereinafter called SGSN) in the current release of the 3GPP core network. The UPE terminates the RAN interface and is in that respect similar to the previously used Gateway Support Node (hereinafter called GGSN) when direct tunnel between the RNC and the GGSN is used. The System Architecture Evolution Gateway (SAE GW) is a node that will contain the main features of the GGSN in current release of the 3GPP network.
One effect of the changed architecture of the Radio Access Network (hereinafter called RAN) is that there will be substantially more radio access nodes, i.e. eNodeBs communicating directly with the core network nodes MME and UPE. This effect is further enhanced when pooling of CN nodes (similar to lu-flex in the legacy 3GPP standard) is applied because an even larger number of eNodeBs will communicate with each MME and UPE.
The cells of LTE radio are expected to be smaller than in legacy 3GPP radio and a moving UE is likely to cause a higher frequency of cell changes. The smaller cells also cause a shorter timing window for a signalling procedure to complete when dealing with a moving UE. The most basic procedure that needs to be functional at these constraints is the intra LTE handover when the UE moves from the control of one eNodeB to the control of another eNodeB.
The increase in the expected number of eNodeBs and the expected reduction of coverage area per eNodeB will result in a substantially larger number of executed handover procedures between eNodeBs as well as between eNodeB and MME and UPE nodes. The hand over procedure therefore need to be efficient to meet requirements of expected characteristics in end-to-end communication between UEs and applications located within or beyond the core network.
There is thus a need for a method and a system that allows for an efficient and fast handover procedure in the above mentioned system.